System and Process for the Combustion of Solid Fuels

ABSTRACT

A system that provides for the efficient combustion of solid fuels is disclosed. The system includes a combustion chamber, a solid fuel dosing system for determining an amount of solid fuel to supply to the combustion chamber, a solid fuel conveying air blower for conveying solid fuel from the solid fuel dosing system to the combustion chamber, and an air combustion fan for supplying air to the combustion chamber via air conveying piping. The system may optionally further include a measurement and auxiliary fuel control system for determining an amount of auxiliary fuel to supply to the combustion chamber. Combustion of the auxiliary fuel raises a temperature of the combustion chamber to a level suitable for combustion of the solid fuel. The combustion chamber may be mounted on a displacement trolley.

BACKGROUND

Solid fuels are less expensive than liquid and gaseous fuels, making them a preferred alternative in many combustion processes.

SUMMARY

Embodiments of the invention relate generally to a system that enables the efficient and self-sustaining combustion of solid fuels, particularly in connection with processes operating at low temperatures where direct injection and burning of solid fuels is not possible.

In accordance with an embodiment of the invention, a system comprises a combustion chamber, a solid fuel dosing system for determining an amount of solid fuel to supply to the combustion chamber, a solid fuel conveying air blower for conveying solid fuel from the solid fuel dosing system to the combustion chamber, and an air combustion fan for supplying air to the combustion chamber via air conveying piping.

The combustion chamber comprises an inner housing and an outer casing fitted around the inner housing so as to form one or more pockets within the combustion chamber into which air is supplied from the air combustion fan. The combustion chamber further comprises one or more tubes that provide for fluid communication between the one or more pockets and an inner compartment of the combustion chamber. A ceramic insulating material may be applied to an inner surface of the inner housing, and a refractory material may be applied to the ceramic insulating material. At least partial combustion of the solid fuel within the combustion chamber produces a combustible gas capable of being ignited.

The system may further comprise a measurement and auxiliary fuel control system for determining an amount of auxiliary fuel to supply to the combustion chamber. Combustion of the auxiliary fuel raises a temperature of the combustion chamber to a level suitable for combustion of the solid fuel.

The combustion chamber may be mounted on a displacement trolley comprising one or more pipes for providing rigidity to the trolley. The trolley may be supported on a displacement rail structure comprising a Hat support bar and a rail bar disposed transversely to the support bar.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional schematic view of a system in accordance with one or more embodiments of the invention.

FIG. 2 is a front view of a system in an operational state in accordance with one or more embodiments of the invention.

FIG. 3 is a side view of the system depicted in FIG. 2.

FIG. 4 is a front perspective view of a combustion chamber in accordance with one or more embodiments of the invention.

FIG. 5 is an exploded rear perspective view of a combustion chamber in accordance with one or more embodiments of the invention.

FIG. 6 is a partial cut front view of a combustion chamber in accordance with one or more embodiments of the invention.

FIG. 7 is a cross-sectional view of a body of a combustion chamber and an enlarged detailed view of the body in accordance with one or more embodiments of the invention.

FIG. 8 is a top view of a combustion chamber assembled on a displacement trolley in accordance with one or more embodiments of the invention.

FIG. 9 is a right lateral view of the combustion chamber and displacement trolley assembly shown in an alternate view FIG. 8.

FIG. 10 is a left side view of the combustion chamber and displacement trolley assembly shown an alternate view in FIG. 8.

FIG. 11 is a from view of the combustion chamber and displacement trolley assembly shown in an alternate view in FIG. 8.

FIG. 12 is an enlarged detailed view of a rail structure that supports the displacement trolley in accordance with one or more embodiments of the invention.

DETAILED DESCRIPTION

Embodiments of the invention relate generally to a system that includes a combustion chamber that enables the combustion of solid fuels, particularly in connection wily processes where the operating temperatures involved are too low to allow for the direct injection and burning of solid fuels. Suitable solid fuels include, but are not limited to petroleum coke, coal, charcoal, charcoal chaff, biomass (bagasse, sawdust, wood, etc), and/or other grinded fuels.

Solid fuels are significantly less costly than liquid and gaseous fuels, and thus, are an attractive alternative fuel choice for many processes, especially those in which fuel cost is an important consideration. Among those processes in which it is desirable to replace liquid and gaseous fuels with solid fuels are processes involving Rotary Dryers, Fluidized Bed Dryers, Rapid Dryers, Rotary Vertical Calciners, Rotary Vertical Furnaces, and so forth.

FIG. 1 depicts a schematic overview of a system for burning solid fuels in accordance with one or more embodiments of the invention. FIGS. 2 and 3 depict front and side views, respectively, of the system depicted schematically in FIG. 1.

Referring to one or more of FIGS. 1 -3, the system comprises a combustion chamber 1, a support structure 2 (which may be a support and displacement trolley) for providing support for at least the combustion chamber 1, a combustion air fan 3, piping 7 for conveying air from the combustion air fan 3 to the combustion chamber 1, a gravimetric solids dosing system 12 for determining an amount of solid fuel to be supplied to the combustion chamber 1, a solid fuel conveying air blower 13, and a measurement and auxiliary fuel control system 16 for determining an amount of auxiliary fuel to be supplied to the combustion chamber.

According to an exemplary embodiment of the invention, prior to burning the solid fuels, an auxiliary fuel which may be a liquid fuel (e.g. diesel oil, bunker oil, etc.) or a gaseous fuel (e.g. natural gas, I.P.G. etc) is supplied from the measurement and auxiliary fuel control system 16 to the combustion chamber 1 to heat the chamber 1 to a sufficiently high internal temperature. Once the chamber is adequately heated, solid fuels can be injected into the chamber and combusted as part of a self-sustaining process.

Solid fuel particles 14, which may be stored in a silo 15, are introduced to a pneumatic conveying line that leads to the combustion chamber 1. The solid fuels 14 may be introduced to the pressurized air circuit by dosing system 12, or in alternative embodiments, by a solids pump or an eductor. A solid fuel conveying air blower 13 (which may be a roots-type blower) supplies air for conveying the solid fuel particles to the combustion chamber 1.

FIGS. 4, 5 and 7 depict various more detailed views of the combustion chamber 1 in accordance with one or more embodiments of the invention. The combustion chamber 1 enables the ignition of solid fuels 14, producing a flame at an outlet of the chamber 1. The solid fuels 14 may comprise one or more materials in a solid phase. The solid fuels 14 may have been grinded, crushed, pulverized, or mechanically altered in some manner prior to being housed in the silo 15. The combustion chamber 1 is typically maintained at an internal temperature of about 2732° C. or above. The high internal temperature of the combustion chamber 1 coupled with pre-heated primary air fed to the chamber 1 and the low dust concentration present in an internal environment of the chamber 1 contribute to the efficient burning of the solid fuels 14.

The combustion chamber comprises an inner housing 4 and an outer casing 5 that is fitted around the inner housing 4 of the chamber 1 so as to form pockets 17. The pockets 17 provide for internal cooling of the inner housing 4 and pre-heating of air used in the centrifugation of solid fuel particles 14 within the chamber 1. The inner housing 4 and/or the outer casing 5 may be constructed from stainless steel and/or formed of carbon steel plates. The combustion chamber 1 may further comprise low density ceramic fiber plates 19 and/or high alumina and low iron oxide content refractory material coaling 18 provided in proximity to the inner housing 4. More specifically, the ceramic plates may be provided adjacent to an inner surface of the inner housing 4. and the refractory material 18 may be applied as a coating to the ceramic plates 19.

In order to obtain and maintain desired conditions within the combustion chamber 1 for the combustion of solid fuels, the system comprises a combustion air fan 3 and primary adjustment air piping 7. The air conveyed through piping 7 can reach manometric pressure levels up to 100 mbar. The combustion air fan 3 comprises a drive motor which may be fed with a variable frequency through the use of a frequency converter. The frequency supplied to the drive motor of the combustion air fan 3 may be altered to adjust the primary air flow to the combustion chamber 1 in dependence on operating conditions of the system.

Air introduced into the pockets 17 formed in the combustion chamber 1 between the inner housing 4 and the outer casing 5 is tangentially injected at high velocities into an inner compartment of the combustion chamber 1 via air injectors 6. The air injectors 6 may be pipes formed of stainless steel. Solid fuel injection may occur through dedicated nozzle(s) such that the solid fuel is injected tangentially in the same rotational direction as the primary air injected through injectors 6. Tangential introduction of the solid fuel 14 into the combustion chamber 1 serves to enhance rotation within the combustion chamber 1, and thus, further improves fuel combustion and gasification. The solid fuel may in certain embodiments also be injected through injectors 6.

The injection of air through pipes 6 generates intense centrifugal rotation of the solid particles 14 within the combustion chamber 1. This centrifugal rotation causes the solid fuel particles 14 to stay close to a periphery of the inner compartment of the chamber 1 as they are consumed, leading to high solid particle residence times with the chamber 1. Processes in accordance with embodiments of the invention thus enable an efficient burn with at least partial combustion of solids into a combustible gas and no remaining residual fuel. The pipes or lubes 6 may be inclined in order to promote tangential injection of primary air. As a result of its structure and its internal geometry, the combustion chamber 1 is capable of retaining, by a centrifugal mechanism, solid fuel panicles (14) introduced to the chamber 1. The chamber 1 allows for the oxidation of all of the solid fuel or a portion thereof and outputs ignited gases and particles through a discharge outlet provided coaxially to the chamber 1.

The system may further comprise a burner nozzle that connects to a gas or oil lance and that is used for preheating the chamber 1 and adjusting the flame as well as a pilot connection point for firing the oil burner. Viewers may also be provided.

According to one or more exemplary embodiments of the invention, the combustion chamber 1 may be supported on a support structure. Referring in particular to FIGS. 11 and 12, the support structure may be a support trolley 2 comprising pipes 11 having a roughly rectangular, square or round-shaped cross-section. The pipes 11 provide increased rigidity to the structure. The support trolley 2 may be assembled or placed on a displacement rail structure 8 comprising a flat support bar 9 and a rail bar 10 that is disposed transversely to the support bar 9 and that has a roughly rectangular or square cross-section. 

1. A system comprising: a combustion chamber: a solid fuel dosing system for determining an amount of solid fuel to supply to the combustion chamber: a solid fuel conveying air blower for conveying solid fuel from the solid fuel dosing system to the combustion chamber: and an air combustion fan for supplying air to the combustion chamber via air conveying piping: the combustion chamber comprising: an inner housing and an outer casing fitted around the inner housing so as to form one or more pockets within the combustion chamber into which air is supplied from the air combustion fan, and one or more tubes that provide for fluid communication between the one or more pockets and an inner compartment of the combustion chamber. wherein at least partial combustion of the solid fuel within the combustion chamber produces a combustible gas capable of being ignited.
 2. The system of claim 1, further comprising: a measurement, and auxiliary fuel control system for determining an amount of auxiliary fuel to supply to the combustion chamber, wherein combustion of the auxiliary fuel raises a temperature of the combustion chamber to a level suitable for combustion of the solid fuel.
 3. The system of claim 1, wherein the solid fuel comprises at least one of: one or more pulverized solids, one or more grinded solids, and one or more crushed solids.
 4. The system of claim 1, the combustion chamber further comprising: a ceramic insulating material applied to an inner surface of the inner housing, and a refractory material applied to the ceramic insulating material.
 5. The combustion chamber of claim 1, wherein the combustion chamber is mounted on a displacement trolley comprising one or more pipes for providing rigidity to the trolley, the trolley being supported on a displacement rail structure comprising a flat support bar and a rail bar disposed transversely to the support bar. 